Based on the Brazilian test results of 23 kinds of transversely isotropic rocks, five trends are obtained for the variation of normalized failure strength (NFS) as a function of the weak plane-loading angles. For each angle, three kinds of fracture patterns are obtained. Furthermore, a new numerical approach based on the particle discrete element method is put forward to systematically investigate the influence of the micro-structure of rock matrix and strength of weak plane on NFS and fracture patterns. The results reveal that the trend of NFS and fracture patterns are slightly influenced by coordination number of rock particles and tensile strength of weak plane, but greatly influenced by percentage of pre-existing cracks and shear strength of weak plane. Micro-parameters of the numerical approach are calibrated to reproduce behaviours of transversely isotropic rocks with different trends, and the simulation results are well matched with experimental results in terms of NFS and fracture patterns. Finally, the numerical approach is applied to study the failure process of layered surrounding rock after tunnel excavation. The simulation results also agree well with observation results of engineering projects. 相似文献
Acta Geotechnica - For deep hard–brittle rock mass engineering in a complicated hydrogeological environment, deformation and damage of the surrounding rock during excavation are often driven... 相似文献
Anchor plate is a necessary component of the prestressed rock bolt, which plays a decisive role in actively resisting the rock mass deformation and improving the self-bearing capacity of the surrounding rock. In this paper, in order to investigate the effect of anchor plate on the mechanical behavior of prestressed rock bolt used in squeezing large deformation tunnel, a series of numerical, field and laboratory tests were performed. The mechanical characteristics of anchor plate with different shapes and sizes were systematically analyzed. Based on the Muzhailing Tunnel in Gansu Province, China, which is a typical deep-buried soft rock tunnel and suffered from serious squeezing large deformation disaster, the field verification was carried out. Meanwhile, the influences of spherical washer on the mechanical behavior of bolt shaft and anchor plate were also investigated. The result shows that the bowl-shaped plate has much better performance than the flat one, while the rounded bowl plate performs slightly better than the squared bowl plate. With the increase of plate thickness or plane size, the anchor plate has the better bearing capacity, while the stress transfer effect will be worse. Furthermore, the non-uniform deformation will gradually increase with the decrease of plate thickness or increase of plane size. Therefore, it is advised to increase the plate thickness rather than the plane size under the condition of better bearing capacity. The bending-induced stress of the anchor plate increases rapidly with the increase of the inclination angle between bolt shaft and anchor plate. Whereas the installation angle is unavoidable in practice, the spherical washer which has great effects on reducing the bending-induced stress could be a necessary component of the prestressed rock bolt system.